body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
}

.header {
    position: relative;
}

.header-image {
    overflow: hidden;
    height: 0;
    transition: height 5s ease-in-out;
}

.header-image img {
    width: 100%;
    height: 400px;
    object-fit: cover;
}

#closeButton {
    position: absolute;
    top: 10px;
    right: 10px;
    background-color: rgba(0, 0, 0, 0.5);
    color: white;
    border: none;
    padding: 5px 10px;
    cursor: pointer;
    z-index: 100;
}

.navbar {
    background-color: #333;
    overflow: hidden;
}

.navbar ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
}

.navbar li {
    float: left;
}

.navbar li a {
    display: block;
    color: white;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
}

.navbar li a:hover {
    background-color: #575757;
}

.accordion {
    width: 100%;
    max-width: 600px;
    margin: 20px auto;
    background-color: #fff;
    border: 1px solid #ddd;
    border-radius: 5px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.accordion-item {
    border-bottom: 1px solid #ddd;
}

.accordion-header {
    background-color: #f7f7f7;
    color: #333;
    cursor: pointer;
    padding: 18px;
    width: 100%;
    text-align: left;
    outline: none;
    transition: background-color 0.6s ease;
    font-size: 18px;
    border: none;
    display: flex;
    align-items: center;
}

.accordion-header:hover {
    background-color: #e0e0e0;
}

.accordion-header i {
    margin-right: 10px;
}

.accordion-content {
    padding: 0 18px;
    background-color: #fff;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.2s ease-out;
}

.content {
    padding: 20px;
}

img {
    display: block;
    margin: 0 auto;
    max-width: 100%;
    height: auto;
}

#backToTopBtn {
    display: none; /* 默认隐藏按钮 */
    position: fixed;
    bottom: 20px;
    right: 30px;
    z-index: 99;
    font-size: 18px;
    border: none;
    outline: none;
    background-color: #555;
    color: white;
    cursor: pointer;
    padding: 15px;
    border-radius: 4px;
}

#backToTopBtn:hover {
    background-color: #777;
}